Manufacture and treatment of leather



Patented Apr. 27, 1926.

UNITED STATES OTTO WALTER, OF HANNOVER, GERMANY.

MANUFACTURE AND TREATMENT OF LEATHER.

No Drawing. Applicationfiled June 2,

To all whom it may concern:

Be it known that I, O'r'ro VVALTER, a citizen of the German Republic, residing at No. 241 Giesenerstrasse, Sarstedt, in 1 Hannover, Germany, have invented certain new and useful Improvements in the Manufacture and Treatment of Leather, of which the following is a specification.

This invention has for its object to provide an improved process for the manufacture of leather capable of withstanding high tensile and compressive strains, and more particularly suitable for use in the manufacture of driving belts, boot sole leather, packing rings, hydraulic cup leathers and the like. The improved process differs from the hitherto known-process for the manufacture of leather by the fact that the raw leather which has been bark-tanned or chrometanned is impregnated in a known manner with a solution of a colloid substance such as glue, gelatine, agar-agar, celluloid, caoutchouc, and, if necessary, with an addition of formaldehyde or the like, preferably by means of a fulling operation, and after being allowed to drain, is set aside for a considerable time, being consequently stretched in a stretching frame in which it is allowed to remain until it has set, that is to say until it no longer contracts either lengthwise or crosswise when removed from the frame.

The leather thus produced is extremely resistant to compression and tension. Its compressive strength can be still further increased by maintaining the leather at a moderate heat during the treatment in the stretching frame, and afterwards, if required, treating it in a known manner in a bath containing a filling substance.

Owing to its resistance to tensile strain, the leather on being taken out of the stretching frame is excellently adapted for the manufacture of driving belts. As is well known, all leathers when subjected to a cer tain load, have the property of becoming temporarily and permanently elongated and stretched. Temporary elongation is necessary for driving belts, whereas permanent elongation is detrimental and gives rise to disturbances in the working of such belts.- Various propositions have already been made with the object of preventing permanent elongation. Chiefiy with this object in view the leather has been stretched under tension is t e we? s ate i ho t h e er Q at g 1924- Serial N0. 717,431.

permanent elongation to a degree satisfactory in practice.

The driving further frequently the defect of curling, that is to say, of unequal elongation of the leather in its longitudinal direction. This defect is likewise obviated by the improved process of the present invention.

The leather produced according to this improved process is however distinguished not only by its tensile strength, but also by its compressive strength, and consequently it,

maybe employed for many purposes, such as for instance, sole leather, packings, hydraulic cup leathers and the like.

A preferred form of the improved process is as follows Bone-glue completely covered with water is left to swell for 48 hours, and the swollen mass is dissolved in the water bath. When set, the mass constitutes the raw material for the preparation of the colloid solution, more especially as the glue keeps in this condition, and especially after it has received an addition of preserving agents and it allows of an exact uniform work.

' 500 grms. of this glue-ielly'are dissolved in 10 litres of water at 6:) to 7Q Centigrade, and then mixed with 100 cubic centimetres of a 10% solution of formaldehyde (40 volumes per cent) with stirring. A fulling vat is now charged with a quantity of this solution corresponding to the quantity of the leather to be treated, and the leather is fulled in this vat, preferably with an admission of hot air of about to 70 centigrade. The impregnated leather-hides on being removed from the fulling vat are allowed to drain, and with frequent turning over are piled up to about 10 hides upon one another, and then allowed t0 rest for about-24 hours.

On the expiration of this period the colbelts hitherto employed have I loids have combined with the fibres, and the 1 leather has acquired a very high degree of suppleness. It is then gradually subjected to tension in the stretching frame so as to stretch the leather by about 10% of its orig-.

inal length. In this stretched condition the leather is allowed to dry until it has set, that is to say, until the dried leather no longer contracts when relieved of tension.

The resulting leather is excellently adapted for the manufacture'of driving belts because it can be temporarily, but not permanen ly e nga d vent 0.75).

Although the resulting leather is also more resistant to compressive strain than leather produced according to the ordinary processes, and is suitable for all purposes, yet its compressive strength can be still further increased by heating it to about 40 centigrade, whilst it is in the stretching frame.

If the leather is to be employed more especially as sole leather it is preferred to add a further treatment for the purpose of incorporating filling substances with it in a known manner. A bath suitable for this purpose may be made up in the form of an ointment from a solution of resin which, after the solvent has been evaporated, causes an incrustation of the fibres of the leather by oxidation of the filling substances which left behind. Excellently suitable for this purpose is a bath made up as follows:

kgs. of colophony are boiled with 1 kg. of linseed oil, or with so much of the latter that a mass of ointment-like consistency remains behind after cooling. To this mass there is added 10% of a tar oil for instance oleum rusci, and the whole is diluted down to a specific gravity of 0.89 with benzol, benzine or the like (specific gravity of the sol- The hides coming from the stretching frame are piled in the liquid thus produced the temperature of which is preferably in-' creased to to centigrade, and are left in the said liquid until they have become completely saturated.

After drying, the leather may be further treated or dressed in a known manner by smoothing, (gliitten) trimming, butting (stossen) etc.

The leather thus produced can be readily worked, and does not swell under the foot by the action of moisture or wet, because it has already acquired in the course of its manufacture an appreciable elongation in all directions. Further, the filling substances can not be washed out of the leather, because they are combined chemically with the latter.

hat I claim is V 1. A process for treating leather for rendering it highly resistant to tensile and compressive strains, consisting in impregnating the raw leather with a solution of a colloid, allowing the impregnated leather to drain and setting it aside to rest, subsequently stretching it iii a stretching frame and causing it to remain stetched .in the said frame until it has set.

2. A process for treating leather for rendering it highly resistant to tensile and compressive strains, consisting in impregnating the raw leather with a solution of a colloid with the addition of formaldehyde, allowing the impregnated leather to drain and setting it aside to rest, subsequently stretching it in a stretching frame 'and causing it to remain stretched in the said frame until it has set.

3. A process for treating leather for rendering it highly resistant to tensile and compressive strains, consisting in impregnating the raw leather by means of a fulling operation, with a solution of a colloid, allowing the impregnated leather to drain and setting it aside to rest, subsequently stretching it in a stretching frame and causing it to remain stretched in the said frame until it has set.

4. A process for treating leather for rendering it highly resistant to tensile and compressive strains, consisting in impregnating the raw leather with a solution of a colloid, allowing the impregnated leather to drain and setting it aside to rest for from 20 to 24 hours, subsequently stretching it in a stretching frame and causing it to remain stretched in the said frame until it has set.

5. A process for treating leather for rendering it highly resistant to tensile and compressive strains, consisting in impregnating the rawlleather with a solution of a colloid, allowing the impregnated leather to drain and setting it aside to rest, subsequently stretching it in a stretching frame, heating the leather to a high temperature (about 25 to C.) while in the said frame and causing it to remain stretched in the said frame until it has set for the purpose set forth.

6. A process for treating leather for rendering it highly resistant to tensile and compressive strains, consisting in impregnating the raw leather with a-solution of a'colloid, allowing the impregnated leather to drain, setting it aside to rest, stretching it in a stretching frame, heating the leather while in the said frame to a high temperature (about 25 to 40 (1.), causing the leather to remain stretched in the sa d frame until it has set, removing the leather from the stretching frame and incorporating a filler with the leather.

7. A process for treating leather for rendering it highly resistant to tensile and compressive strains, consisting in impregnating the raw leather with a solution of a colloid, allowing the impregnated leather to drain, setting it aside to rest, stretching it in a stretching frame, heating the leather while in the said frame to a high temperature (about 25 to 40 C.), causing the leather to'remain stretched in the said frame until it has set, removing the leather from the stretching frame and incorporating a filler consisting of a solution of resin with the leather.

In testimony whereof, I have signed my name to this specification.

OTTO WALTER. 

